Growth promoter for aquatic plant and method for application thereof

Abstract: The use of phosphate to promote growth of aquatic plants and a method for providing the growth promoter which comprises placing an aqueous solution or dispersion of phosphate in a container having at least one opening, and placing the container in water in a water tank thereby to allow the phosphate to pass through the opening into the water.

Description: The present invention relates to a method for promoting the growth of aquatic plants which increases the carbonate ion concentration in a water tank with aquatic plants therein (e.g., a fish tank or aquarium) up to a concentration which promotes the growth of the aquatic plants, which thereby activates the photosynthesis of the aquatic plants. It is known that the optimum carbonate ion concentration for the growth of aquatic plants is 15 to 16 ppm. However, tap water and underground water, for example, generally have a carbonate ion concentration of 4 to 6 ppm. To promote the growth of aquatic plants it is effective to increase the carbonate ion concentration in the water. For increasing the carbonate ion concentration, there is known a method in which carbon dioxide is gradually introduced into the water from a container filled with carbon dioxide. Problems with this method are that additional equipment such as the above container is required and that the handling of such equipment is complicated. Another problem with the above method is that since carbon dioxide gas rapidly rises upwards in water, the effect on the growth of aquatic plants is not as good as expected. Furthermore, when the equipment is handled carelessly, all the carbon dioxide may be released at once, which alters the aquatic environment. As a result, fish, kept together with the aquatic plants may be harmed. The present invention provides the a method for promoting the growth of aquatic plants in a water tank by converting the carbonates and bicarbonates present as permanent hardness components in water in said tank to phosphates and by using the carbonate and bicarbonate ions formed as a source of a carbonate component for the promotion of growth of said aquatic plants, which comprises placing (a) an alkali metal salt or ammonium salt of orthophosphoric acid and (b) an alkali metal salt or ammonium salt of polyphosphoric, metaphosphoric or pyrophosphoric acids, in effective amounts in said tank. In the present invention the carbonate ion concentration in water in a water tank is increased, thereby promoting the growth of aquatic plants. The first phosphate used in the present invention is a primary alkali metal or ammonium salt of orthophosphoric acid (M 1 H 2 PO 4 ), secondary alkali metal or ammonium salt of orthophosphoric acid (M 1 2 HPO 4 ) or tertiary alkali metal or ammonium salt of orthophosphoric acid (M 1 3 PO 4 ). The second phosphate is an alkali metal or ammonium polyphosphate (M 1 n+1 P n O 3n+1 ), metaphosphate ((M 1 PO 3 ) n ) or pyrophosphate acid salt (M 1 2 H 2 P 3 O 7 ). In the above chemical formulae, M 1 is an alkali metal such as sodium or potassium, or ammonium. Carbonate ions dissolved in water form carbonates or bicarbonates with metal ions in the water. The metal ions include alkali metal and alkaline earth metal ions. In the present invention, the carbonate is brought into a state where carbonate ions can be easily released by chelating the alkaline earth metal ions with phosphate, i.e., masking the alkaline earth metal ions of the carbonate or bicarbonate. The orthophosphoric acid salts, including primary, secondary and tertiary salts of orthophosphoric acid, used in the present invention forms a sparingly soluble salt with alkaline earth metals to mask the alkaline earth metals. The polyphosphate, metaphosphate and pyrophosphates used in the present invention form a water-soluble complex with alkaline earth metals to mask the alkaline earth metals. In view of the appearance of the water tank a phosphate which forms a water-soluble complex is used. A phosphate which forms a sparingly soluble salt can be used together with the phosphate which forms a water-soluble complex, since, in this case, the amount of precipitate is small. Calcium or magnesium, which form carbonates or bicarbonates when in the form of metal ions, are hardness components and are contained in water. Furthermore, when living organisms such as plants and fish are present, calcium and magnesium are also contained in their food and excretions. The metal ions are present as a carbonate hardness component or a non-carbonate hardness component. The non-carbonate hardness component is present in the form of a sulfate or chloride. Since a large amount of carbon dioxide in air is dissolved in the water, the carbonate hardness component is present in a larger amount. The chelating effect of the phosphate on the carbonate hardness component is as follows when the phosphate is a tertiary salt of orthophosphoric acid: 3Ca(HCO 3 ) 2 + 2Na 3 PO 4 → Ca 3 (PO 4 ) 2 + 6NaHCO 3 3Mg(HCO 3 ) 2 + 2Na 3 PO 4 → Mg 3 (PO 4 ) 2 + 6NaHCO 3 3CaCO 3 + 2Na 3 PO 4 → Ca 3 (PO 4 ) 2 + 3Na 2 CO 3 3MgCO 3 + 2Na 3 PO 4 → Mg 3 (PO 4 ) 2 + 3Na 2 CO 3 The carbonate, sulfate, nitrate and chloride of calcium or magnesium are sparingly soluble, and are present as permanent hardness components, while the sodium salts of carbonic acid or bicarbonic acid are water-soluble, and are present as free carbonates. The present invention seeks to convert the carbonate and bicarbonates present as permanent hardness components to phosphates and to use the carbonate and bicarbonate ions formed as a source of a a carbonate component for the promotion of growth of aquatic plants. In free carbonates in water, carbonate and bicarbonate ions maintain a quantitative equilibrium state depending upon the pH. When carbonate ions are absorbed into plants, bicarbonate ions are converted to carbonate ions. When carbonate ions and bicarbonate ions are in an equilibrium state, and when the pH is 6.5 or less, the amount of carbonate ions is larger than the amount of bicarbonate ions. The optimum pH for freshwater aquarium fish is about 6.8. To maintain a pH of about 6.8, a plurality of phosphates may be used in combination to impart the growth promoter with a pH buffer capability. An aqueous solution or dispersion of the agent may be placed in a container having at least one narrow opening. The container is then placed in water in a water tank thereby to allow the phosphates to pass through the opening into the water. The form of the above "container" is not specially limited. It is preferred to use a container having a proper volume, having the form of, or a form similar to the form of, for example, an ampoule to be filled with an injection solution, and having at least one narrow opening. The container may have at least one narrow opening in any place on the container, for example at one terminal end. The growth promoter is placed in the above container, and the growth promoter is allowed to ooze through the narrow opening. This container may be horizontally, vertically or obliquely positioned in a water tank, since the growth promoter easily oozes through the narrow opening due to a difference between the concentration within the container and the concentration outside the container. For allowing the growth promoter to ooze easily, it is preferred to position the container in a water tank such that the narrow opening faces downward. The container may contain not only the growth promoter but also a water-soluble or water-dispersible fertilizer. The growth promoter for aquatic plants used in the present invention chelates sparingly soluble carbonate in water to convert it into advantageous carbonate, which carbonate can be used for the promotion of growth of aquatic plants. The growth promoter may be gradually released into the water, whereby the change of an environment in water proceeds only gradually. In this way fish such as aquarium fish which are often kept together with aquatic plants are not harmed. The present invention will now be further described in the following Examples. In the Examples percentages are by weight unless otherwise specified. Example 1 Three water tanks having a size of 60 x 36 x 30 cm were each filled with 55 liters of water, and the following test conditions were set: Tank A: A container containing 30 ml of an aqueous solution containing 3 % of primary potassium phosphate, 6 % of secondary sodium phosphate and 10 % of sodium metaphosphate was placed in the first water tank such that the narrow open end of the container faced downwards. Tank B: 400 milliliters of carbon dioxide gas was dissolved in the water of a second tank once a day by releasing the carbon dioxide into a cylindrical diffuser having a diameter of 6 cm and a height of 17 cm, which had an opening facing downward. The dissolved carbonate gradually diffused through the lower portion of the diffuser into the water in the water tank. The release of carbon dioxide was carried out at 9:30 am every day. The pH of the water in each tank was measured at 4:30 pm every day. Tank C: A third tank was filled with water alone. The temperature of the water in each tank was set at 25 to 28°C, and, as aquatic plants, 10 pieces of Cabomba Caroliniana having a height of approximately 15 to 20 cm and 10 pieces of Ludwigis Repens having a height of approximately 10 to 12 cm were placed in each tank. The water in each tank was filtered through an air-lift filter, and exposed to two 20 W fluorescent lamps for plant growth for 10 hours per day. The water in each tank was measured for dissolved carbonate concentration, pH and total hardness. Table 1 shows the results. In each tank, for evaluating the degrees of growth of the aquatic plants, the heights of the aquatic plants were measured excluding the lengths of their root portions 14 days after the test was initiated. Table 2 shows the results, in which the figures show the numbers of aquatic plants having the heights shown in a left column. 0 1 2 3 4 5 6 7 (days) Tank A pH 7.8 7.3 7.5 7.6 7.6 7.6 7.7 7.6 Dissolved carbonate concentration 4 18 18 18 18 18 16 16 Total hardness 75 65 65 65 65 65 65 65 Tank B pH 7.8 7.4 7.5 7.6 7.5 7.4 7.3 7.5 Dissolved carbonate concentration 4 6 6 6 6 6 6 6 Total hardness 75 70 70 70 70 70 70 70 Tank C pH 7.8 7.8 7.8 8.1 8.1 7.8 7.8 8.0 Dissolved carbonate concentration 4 4 4 4 4 4 4 4 Total hardness 75 74 74 75 75 75 75 75 Notes: Unit of dissolved carbonate concentration: ppm Unit of total hardness: ppm 8 9 10 11 12 13 14 (days) Tank A pH 7.6 7.5 7.5 7.6 7.6 7.5 7.5 Dissolved carbonate concentration 16 16 16 16 16 16 16 Total hardness 65 65 65 65 65 65 65 Tank B pH 7.7 7.7 7.8 7.9 8.1 8.0 8.0 Dissolved carbonate concentration 6 6 6 6 6 6 6 Total hardness 70 70 70 70 70 70 70 Tank C pH 7.9 7.9 8.0 8.1 8.0 7.9 7.9 Dissolved carbonate concentration 4 4 4 4 4 4 4 Total hardness 75 75 75 75 75 75 75 Notes: Unit of dissolved carbonate concentration: ppm Unit of total hardness: ppm Height of Cabomba Caroliniana (cm) Tank A Tank B Tank C 15 - 20 cm 0 1 5 21 - 25 cm 3 8 5 26 - 30 cm 7 1 0 Height of Ludwigis Repens (cm) Tank A Tank B Tank C 10 - 12 cm 0 2 1 13 - 15 cm 6 5 8 16 - 18 cm 4 3 1 In tank A in which the growth promoter of the present invention was added, the pH was relatively stable for 14 days in a state in which the pH was decreased. Further, the total hardness was also stable for 14 days in a state in which it was lower than that found before the growth promoter was added. Furthermore, the dissolved carbonate concentration was stable for 14 days, i.e., it was 16 to 18 ppm. Moreover, as compared with the other tanks, a remarkable growth of the aquatic plants was observed. When changes in water quality, such as a change in the pH, were measured every hour, it was found that the water quality changed only gradually. This shows that the environmental influence of the growth promoter on fish can be minimized. Example 2 Changes in water quality were studied in the same manner as in Example 1 except that the amounts of phosphates added to tanks were changed as shown below (tanks D and E). Tank D Tank E Sodium metaphosphate 3 % 10 % Secondary sodium phosphate 6 % 9 % Primary potassium phosphate 10 % 0 % Further, carbon dioxide gas was introduced in the same manner as in Example 1 (tank F), and a tank was filled with water alone (tank G). The results are shown in Table 3. 0 1 2 3 4 5 6 7 (days) Tank D pH 8.1 7.4 7.6 7.8 7.7 7.6 7.8 7.8 Dissolved carbonate concentration 4 16 16 14 14 14 14 12 Total hardness 80 70 70 70 70 75 75 75 Tank E pH 8.1 7.5 7.7 7.9 7.9 7.8 8.0 7.9 Dissolved carbonate concentration 4 10 10 8 8 8 8 8 Total hardness 80 70 70 70 70 75 75 75 Tank F pH 8.1 8.0 7.8 7.9 7.8 8.0 7.9 7.9 Dissolved carbonate concentration 4 6 6 6 6 6 6 6 Total hardness 80 80 80 80 80 80 80 80 Tank G pH 8.1 8.0 8.0 8.1 8.2 8.2 8.2 8.1 Dissolved carbonate concentration 4 4 4 2 2 2 2 2 Total hardness 80 80 80 80 80 80 80 80 Notes: Unit of dissolved carbonate concentration: ppm Unit of total hardness: ppm 8 9 10 11 12 13 14 (days) Tank D pH 7.7 7.7 7.7 7.7 7.8 7.7 7.7 Dissolved carbonate concentration 12 12 12 12 12 12 12 Total hardness 75 75 75 75 75 75 75 Tank E pH 7.8 7.8 7.9 7.8 7.9 7.8 7.8 Dissolved carbonate concentration 8 8 8 8 8 8 8 Total hardness 75 75 75 75 75 75 75 Tank F pH 8.0 7.9 7.8 7.9 7.7 7.9 7.9 Dissolved carbonate concentration 6 6 6 6 6 6 6 Total hardness 80 80 80 80 80 80 80 Tank G pH 8.1 8.1 8.2 8.2 8.1 8.0 8.1 Dissolved carbonate concentration 2 2 2 2 2 2 2 Total hardness 80 80 80 80 80 80 80 Notes: Unit of dissolved carbonate concentration: ppm Unit of total hardness: ppm In each of tanks D and E, the dissolved carbonate concentration was from 8 to 16 ppm, and the carbonate concentration was maintained in the range suitable for growing aquatic plants.

Claims: A method for promoting the growth of aquatic plants in a water tank by converting the carbonates and bicarbonates present as permanent hardness components in water in said tank to phosphates and by using the carbonate and bicarbonate ions formed as a source of a carbonate component for the promotion of growth of said aquatic plants, which comprises placing (a) an alkali metal salt or ammonium salt of orthophosphoric acid and (b) an alkali metal salt or ammonium salt of polyphosphoric, metaphosphoric or pyrophosphoric acids, in effective amounts in said tank. A method according to claim 1, wherein the alkali metal salts are sodium or potassium salts. A method according to claim 2 where an agent containing primary potassium phosphate, secondary sodium phosphate and sodium metaphosphate is placed in said task. A method according to any one of the preceding claims, which comprises placing an aqueous solution or dispersion of the agent in a container having at least one opening, and placing the container in water in said tank thereby to allow the phosphate to pass through the opening into the water. A method according to claim 4, wherein the agent is allowed to diffuse through a narrow opening at one terminal end of the container. A method according to claim 4 or 5, wherein the container is placed in the tank such that the opening opens downwards.

Inventors: YOSHIDA NOBUYUKI, YOSHIDA, NOBUYUKI, YOSHIDA, NOBUYUKI, C/O JAPAN PET DRUGS CO. LTD.
Applicants: JAPAN PET DRUGS CO LTD, JAPAN PET DRUGS CO., LTD.
Application year: 1994
Main classification: C05B3
IPC codes: C05B3, C05D7, A01G33, A01N59, C05B7, C05B21